Air bag device

Abstract

An air bag device having a switch adapted to be operated when a breakable cover member covering an air bag module mounted in the steering wheel is pushed. Particularly, H-shaped tear lines, including grooves of a V-shape in section, are defined in an inner surface of the cover member. The tear lines are broken by a pressure resulting from the expansion of the air bag to open a lid defined in the cover member. A pair of ridges are integrally formed on the cover member astride a central one of the tear lines. The rigidity of the rear cover member is enhanced by the ridges, whereby the deformation of the cover member is prevented. Thus, the cover member can be slid smoothly to ensure the reliable operation of the switch.

We claim:  
     
         1 . An air bag device for a vehicle comprising: 
 an air bag module including an air bag and an inflator formed integrally with each other,    a module-supporting member mounted at a central portion of a steering wheel for supporting said air bag module,    a cover member slidably supported on the module-supporting member to cover said air bag module,    a switch which operates when the cover member is pushed and slid relative to the module-supporting member, and    groove-shaped tear lines formed in an inner surface of the cover member, so that said air bag, as expanded by a high-pressure gas generated by said inflator upon collision of the vehicle breaks the cover member along the tear lines to deploy into a passenger compartment of the vehicle,    said cover member having at least one ridge integrally formed on the inner surface thereof astride at least one of the tear lines.    
     
     
         2 . An air bag device according to  claim 1 , wherein a groove is defined in a side face of said ridge and extends to a bottom of said at least one tear line.  
     
     
         3 . An air bag device for a vehicle comprising: 
 an air bag module including an air bag and an inflator formed integrally with each other,    a module-supporting member mounted at a central portion of a steering wheel for supporting said air bag module,    a cover member slidably supported on the module-supporting member to cover said air bag module,    a switch which operates when the cover member is pushed and slid relative to the module-supporting member, and    groove-shaped tear lines formed in an inner surface of the cover member, so that said air bag expanded by a high-pressure gas generated by said inflator upon collision of the vehicle breaks the cover member along the tear lines to deploy into a passenger compartment of the vehicle,    said cover member having reinforcing ribs integrally formed on the inner surface thereof, so that they do not intersect the tear lines.    
     
     
         4 . An air bag device according to  claim 3 , wherein at least a portion of said reinforcing ribs extend along at least one of said tear lines.  
     
     
         5 . An air bag device according to  claim 1 , wherein said at least one tear line extends across a central portion of said cover member.  
     
     
         6 . An air bag device according to  claim 5 , wherein said at least one ridge is disposed at an intermediate portion of said at least one tear line.  
     
     
         7 . A cover member for an air bag device disposed with a steering wheel having an activating switch provided therewith, the air bag device including an air bag module having an air bag and an inflator formed integrally with each other, a module-supporting member mounted at a central portion of the steering wheel for supporting said air bag module, wherein: 
 said cover member is slidably supported on the module-supporting member to cover said air bag module and said switch,    said cover member operates said switch when the cover member is pushed and slid relative to the module-supporting member,    said cover member has groove-shaped tear lines formed in an inner surface thereof to assure that said air bag reliably breaks the cover member along the tear lines when it is inflated by said inflator, and    said cover member has at least one rigidity enhancing member integrally formed on the inner surface thereof to assure sufficient rigidity of the cover member during normal use.    
     
     
         8 . A cover member according to  claim 7 , wherein said rigidity enhancing member comprises a ridge integrally formed on the inner surface of the cover member astride one of the tear lines.  
     
     
         9 . A cover member according to  claim 8 , further including a groove defined in a side face of said ridge for assuring that said ridge breaks together with said tear line upon inflation of the air bag.  
     
     
         10 . A cover member according to  claim 8 , wherein said ridge extends to a bottom of said tear line.  
     
     
         11 . A cover member according to  claim 8 , wherein said one of the tear lines extends across a central portion of said cover member.  
     
     
         12 . A cover member according to  claim 8 , wherein said ridge is disposed at an intermediate portion of said one tear line.  
     
     
         13 . A cover member according to  claim 7 , wherein said rigidity enhancing member comprises a reinforcing rib integrally formed on the inner surface of the cover member, said reinforcing rib does not intersect said tear lines.  
     
     
         14 . A cover member according to  claim 13 , including a plurality of said reinforcing ribs integrally formed on the inner surface of the cover member, said reinforcing ribs do not intersect said tear lines.  
     
     
         15 . A cover member according to  claim 14 , wherein at least portions of said reinforcing ribs extend along at least one of said tear lines.  
     
     
         16 . A cover member according to  claim 14 , wherein at least portions of said reinforcing ribs extend substantially perpendicular to least one of said tear lines.  
     
     
         17 . An air bag device according to  claim 1 , wherein said reinforcing ribs substantially surround those of said tear lines disposed in a central portion of said cover member.